Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 210217 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 1017 PM EDT Fri Oct 20 2017 .SYNOPSIS... Warm temperatures and dry conditions are expected through the weekend. A strong cold front will bring the likelihood for showers and thunderstorms later Monday into Tuesday. Much cooler temperatures are expected during the middle of next week as dry weather returns. && .NEAR TERM /THROUGH SATURDAY/... As of 1000 PM Saturday...High pressure aloft will be centered just south of the area while at the surface, high pressure will ridge down the eastern seaboard through the period. This will bring clear skies and virtually calm winds tonight. The low levels are again not particularly susceptible to fog given the lack of moisture. However, similar to last night, strong radiational cooling should allow fog prone locations to experience patchy fog, mainly within an hour or two of daybreak. Lows will be in the 50s, coolest inland where a few upper 40s will be sprinkled. Models are showing precipitable water values remaining between 0.50 and 0.75 inches and the time heights are not showing distinct layers of clouds developing on Saturday and so our forecast will continue to advertise sunny skies. Highs on Saturday will range from the upper 70s at the beaches to the lower 80s inland. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 300 PM Friday...Ridging sfc and aloft will dominate the FA weather Sat night thru Sunday. Skies will mainly be clear with mainly thin Cirrus overhead. Some increase in the low level moisture, below 850mb, from onshore flow will likely be enough for diurnal Cu with possible onshore movement of Stratocu especially across the southern portions of the ILM CWA. For Sun night, the upper ridge axis slides further off the Southeast U.S. coast allowing more opaque cirrus to move overhead. The center of the sfc high just off the Mid-Atlantic States Sat night will slide well offshore Sun thru Sun night but will continue to ridge back across the FA. Flow thruout this period will be onshore with a slow veering trend from ENE at the start of the period to ESE at the end of this period. This will further increase the low level moisture in the form of low level clouds. A weak low-mid level impulse riding up the backside of the upper ridge across SC during Sun may interact with just enough low level moisture for possible low topped showers to occur. However, have kept a dry fcst across the FA, keeping the chance of rain just south and west of the SC portions of the ILM CWA. Onshore flow will limit max temps but nevertheless, low 80s for Sun highs and widespread 50s for Sat night lows and widespread 60s for Sun night lows due to the deeper onshore flow across SSTS that are in the 70s. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 300 PM Friday...Week begins with highly amplified pattern over the eastern CONUS. Deep 5h trough, which may or may not become briefly cutoff, will be over the Mississippi Valley Mon morning and steadily moving east, pushing a cold front with it. Mid-level ridging along the Southeast will also shift east, but the rate at which these features move ultimately determines when showers and thunderstorms ahead of and along the front reach the area. Strong warm advection ahead of the front will push temps close to 10 degrees above normal Mon while ensuring abundant moisture. Still to early to say if strong or severe storms are a threat but low level jet Mon night and Tue will be 40-50 kt so at least some potential exists. Front crosses the area during Tue but cold advection will be delayed and temps will be near to slightly above climo. A shortwave dropping southeast across the western Great Lakes and into the OH/KY Valleys Tue night drives a cold surge into the southeast Wed. Cold advection will drop 850 temps from low teens late Tue to near zero Wed night, ushering in a 36 to 48 hour period of temperatures 5 to 10 degrees below climo. Mid-level trough axis shifts off the coast Thu morning and lifts northeast during the day. Warm advection will already be under way at this point but cold air will linger at the surface through Thu. Thu night or Fri will see temperatures return to levels typical of late October in the southeast. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... As of 23Z...High confidence of VFR at all sites through 21/00Z, with the exception perhaps of a small window for MVFR between 06z to 10z at KILM...KMYR...KFLO and KLBT and as early as 02z at KCRE like last night. There is also a chance of IFR at KLBT between 07z to 11z. Not much in the way of moisture around but just enough in the low levels that with clear skies and calm to light winds we could see some fog developing as a result of radiational cooling. After daybreak VFR with mainly clear skies and light winds. Extended Outlook...Showers and thunderstorms may result in flight restrictions Mon-Tue. && .MARINE... NEAR TERM /THROUGH SATURDAY/... As of 1000 PM Friday...High pressure will continue to be the main influence across the waters. Winds will be under 10 kt overnight as they back to the NE. An ENE wind direction will prevail on Sat with wind speeds increasing to 10 to 15 kt during the afternoon. Seas will be 2 to 3 ft as the easterly swell continues to wane. SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 300 PM Friday...This period will continue to be favorable for Mariners navigating across the local waters. Onshore flow will highlight this period, starting from the NE-ENE Sat night veering slightly thru the period to ESE-SE by Monday morning. This in response to the sfc high`s center migrating from the Mid- Atlantic Coast Sat night to well offshore by Mon morning. The sfc ridging from the high will extend inland from the coast resulting in the onshore flow. The sfc pg will remain relaxed at the start of this period with around 10 kt for speeds. The sfc pg will begin to tighten-some Sun thru Sun night resulting in 10 to 15 kt speeds, except closer to around 15 kt for the southernmost waters. Significant seas will run 2 to 3 ft Sat night followed by a slow 1 foot building trend thru Mon morning when seas will run 3 to 4 ft except around 4 ft southernmost waters. Dominant periods thruout this time-line will run 8 to 9 seconds due to a persistent ESE ground swell. LONG TERM /MONDAY THROUGH WEDNESDAY/... As of 300 PM Friday...Cold front approaching from the west will lead to increasing southerly flow on Mon. Winds start out east- southeast 10 to 15 kt but turn more southerly during the day, increasing to a solid 15 kt later in the day. Winds peak at 20 to 25 kt late Mon night and continue in the 20 to 25 kt range into Tue evening before dropping under 20 kt Tue evening/night and shifting to offshore as the front passes. Seas ahead of the front will build to 5 to 7 ft Mon night and exceed 8 ft in places on Tue. Headlines will likely be raised early Mon night and continue through Tue and into the first part of Tue night. Combination of offshore flow and decreased speeds late Tue night and Wed should allow conditions to drop below headline thresholds. Cold advection following the front is delayed so offshore flow will not be strong right behind the front. However cold air is expected to arrive near the end of the period and offshore winds approach 20 kt Wed night. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...RJD/DRH SHORT TERM...DCH LONG TERM...III AVIATION...MAC

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